1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that can minimize the size of the liquid crystal display device by modifying the structure of a receptacle assembly for receiving a back light assembly and a display unit of the liquid crystal display device.
2. Description of the Related Art
Recently, information processing devices have been developed so as to have various shapes, various functions, and rapid information processing speeds. The information which has been processed by such an information processing device has electrical signals. A display device that functions as an interface is usually used for confirming the information processed by the machine with the naked eye.
Recently, a liquid crystal display device has developed to be lighter and smaller than a display device of a CRT type and to have full spectrum of colors and high resolutions. As the result, a liquid crystal device has been widely used as a monitor of a computer, a television, and a display device of another information processing device.
A liquid crystal display device applies a voltage to an electrode to change the molecular arrangement of the liquid crystal layer. The liquid crystal display device changes the optical properties of liquid crystal layers that pass light according to the molecular arrangement, and uses the modulation of the light of the liquid crystal cells.
Liquid crystal display devices can be categorized into a TN (Twisted Nematic) type and an STN (Super-Twisted Nematic) type. Further, liquid crystal display devices can also be categorized into an active matrix display type that uses a switching device and a TN liquid crystal and a passive matrix display type that uses an STN liquid crystal according to the driving methods.
The active matrix display type is used in a TFT-LCD, and drives an LCD by using a TFT as a switch. The passive matrix display type does not use any transistors, and thus does not need complex circuits that are related to a transistor.
Further, according to the light source, liquid crystal display devices are categorized into a transmission-type liquid crystal display device that uses a back light and a reflection-type liquid crystal display device that uses an exterior light source.
The transmission-type liquid crystal display unit is heavy and voluminous because of the back light, but is widely used because it can be used anywhere without considering the ambient light.
FIG. 1 is an exploded perspective view for showing a conventional liquid crystal display device. FIG. 2 is a cross-sectional view for showing the assembled liquid crystal display device of FIG. 1.
Referring to FIGS. 1 and 2, the liquid crystal display device 600 comprises a liquid crystal display module 700 for displaying a screen by applying a video signal, and a front case 800 and a rear case 900 that receive the liquid crystal display module 700.
The liquid crystal display module 700 comprises a display unit 710 that comprises a liquid crystal display panel. The display unit 710 comprises a liquid crystal display panel 712, an integrated printed circuit board 714, a data side tape carrier package 716, and a gate side flexible circuit board 718 which is manufactured by a COF method.
The liquid crystal panel 712 comprises a thin film transistor substrate 712a, a color filter substrate 712b, and a liquid crystal layer therebetween (not shown).
The thin film transistor substrate 712a is a transparent glass substrate in which thin film transistors of the matrix type are formed. A data line is connected to source terminals of the thin film transistors, and a gate line is connected to gate terminals. A pixel electrode of indium tin oxide (ITO), which is transparent conductive material, is formed in the drain terminal.
If electrical signals are inputted to the data line and the gate line, the electrical signals are inputted to the source terminals and the gate terminals of the thin film transistors. The thin film transistors are turned on or off by the inputting of the electrical signals to the gate terminals. Then, the drain terminal outputs the electrical signals that are needed for showing images at the pixels.
The color filter substrate 712b is opposite to the thin film transistor substrate 712a. The color filter substrate is a substrate in which RGB pixels are formed by the thin film process. A common electrode of the ITO is coated on the front surface of the color filter substrate 712b. 
If a voltage is applied to the gate terminals and the source terminals of the transistors of the thin film transistor substrate 712a and the thin film transistors are turned on, an electric field is formed between a pixel electrode and the common electrode of the color filter substrate. The arrangement of liquid crystal injected between the thin film transistor substrate 712a and the color filter substrate 714b changes by the electric field, and the transmittance of light changes as the arrangement varies.
A driving signal and a timing signal are applied to the gate line and the data line of the thin film transistor to control the arrangement of the liquid crystal of the liquid crystal panel 712 and the timing of when the liquid crystal is arranged. As shown in the figures, a tape carrier package 716 which is a sort of flexible circuit board for determining the data driving signal application time is attached to the source side of the liquid crystal display panel 712, and a gate side flexible circuit board 718 which is manufactured by the COF method for determining the gate driving signal application time is attached to the gate side.
The integrated printed circuit board 714 for receiving the video signals from the outside of the liquid crystal panel 712 and for applying the driving signals to the gate line and the data line is connected to the tape carrier package 714 of the data line side of the liquid crystal display panel 712. The integrated printed circuit board 714 has a source portion to which the video signals generated in an exterior information processing device (not shown) is applied to provide the data driving signals to the liquid crystal display panel 712 and a gate portion for providing the gate driving signals to the gate line of the liquid crystal display panel 712. The integrated printed circuit board 714 generates the gate driving signals for driving the liquid crystal display device, the data signals, and a plurality of timing signals for applying the gate driving signals and the data signals. The gate driving signals are applied to the gate line of the liquid crystal display panel 712 through the gate side flexible circuit board 718, and the data signals are applied to the data line of the liquid crystal display panel 712 through the data tape carrier package 716.
A back light assembly 720 for providing a uniform light to the display unit 710 is provided under the display unit 710. The back light assembly 720 comprises a linear lamp 722 for generating the light. The linear lamp 722 is provided on one side of the liquid crystal display module 700. A light guide plate 724 has a size corresponding to the liquid crystal panel 712, and is located under the liquid crystal panel 712. The lamp side of the light guide plate 724 is the thickest. The thickness gradually decreases as goes away from the lamp 722. The light guide plate 724 guides the light generated in the lamp 722 towards the display unit 710, and changes the passage of the light.
A plurality of optical sheets 726 for making the luminance of the light which is irradiated from the light guide plate 724 and goes towards the liquid crystal display panel 712 uniform is provided above the light guide plate. A reflection plate 728 provided under the light guide plate 724 reflects the light leaked from the light guide plate and improves the efficiency of the light. The display unit 710 and the back light assembly 720 is supported by a mold frame 730 which is a receiving container. The mold frame 730 has a box-like shape, and the upper portion of the mold frame 730 is open. The mold frame 730 comprises four side walls and a bottom surface, and opening portions for bending the integrated printed circuit board 714 along the outer side surface of the mold frame 730 and positioning the integrated printed circuit board 714 are formed in the bottom surface.
A chassis 740 bends the integrated printed circuit board 714 of the display unit 710 and the gate tape carrier package 718 to the outside of the mold frame 730, and fixes the integrated printed circuit board 714 and the gate tape carrier is package 718 to the bottom surface portion of the mold frame 730. The chassis 740 prevents the deviation of the display unit 710. The chassis 740 has a cubic shape like the mold frame 730, and the upper portion of the chassis 740 is open to expose the liquid crystal display panel 710. The side wall portion of the chassis 740 is vertically bent towards the inner side thereof to cover the peripheral portion of the upper surface of the liquid crystal display panel 710.
A bottom chassis 750 is provided in the mold frame 730 to positively fix the back light assembly 720 at a designated position. The bottom chassis 750 has a recessed portion at the central portion thereof to press the bottom surface of the back light assembly and fix the back light assembly 720. Therefore, the area of the liquid crystal display device is increased by the existence of the bottom chassis 750, and the number of the assembling processes for bottom chassis 750 increases. Thus, the manufacturing cost of the liquid crystal display device 100 also increases.
The display unit 710 and the back light assembly 720 is received in the mold frame 730, and the mold frame 730 is thin so as to reduce the size of the liquid crystal display device, and has four side surfaces and one bottom surface. When the mold frame 730 is manufactured using a die, variations in the side surfaces and the bottom surface of the mold frame distort the mold frame 730, which costs lots of trial and errors and manufacturing time.
Further, if a portion of the mold frame 730 is changed, the overall shape of the mold frame 30 should be restructured and the improvement of the mold frame 730 is difficult to improve. Furthermore, recently, since the liquid crystal display device becomes light and thin and as the mold frame of the lamp side becomes thinner, the mold frame cannot be molded easily and the distortion of the mold frame causes serious problems.